While an HFC-based refrigerant is used for refrigeration cycle apparatuses, there is a problem that a HFC-based refrigerant has high global warming potential. As a result, leakage of refrigerant from a refrigeration cycle apparatus has a significant effect on global warming. Accordingly, a technique of reducing the amount of refrigerant to be sealed in the refrigeration cycle apparatus is required.
During operation of the refrigeration cycle apparatus, since a major part of refrigerant sealed in the refrigeration cycle apparatus is stagnated in the heat exchanger, it is important to reduce the amount of stagnating refrigerant by reducing the volume of the heat-transfer tubes of the heat exchanger.
In some conventional heat exchangers, a plurality of rows of heat-transfer tubes are formed of a combination of flat tubes and circular tubes so as to improve heat exchange efficiency (see Patent Literature 1).